


Undertale oneshots

by Vivalavidapasta



Category: Undertale
Genre: ABO, AGONYYYYY, Alcohol, Alpha/Beta/Omega Dynamics, Breeding Kink, F/M, Flirting, Impregnation, It’s a quarter after 1 I’m all alone, Lamias, Longing, M/M, Mating Cycles/In Heat, Nesting, Obsession, Obsessive Behavior, One-Sided Attraction, Oviposition, Pining, Sans does crime, Undertale Skeletons in Heat, Yearning, cliff jumping, funny haha, implied alcohol, implied suicide, one shots, requests open, talking about suicide
Language: English
Status: In-Progress
Published: 2020-02-18
Updated: 2020-04-19
Packaged: 2021-02-28 00:08:06
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 2,130
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22784596
Author URL: https://archiveofourown.org/users/Vivalavidapasta/pseuds/Vivalavidapasta
Summary: Gimme requests and I’ll randomly choose em
Relationships: Sans/Reader, Sans/Sans (Undertale)
Comments: 25
Kudos: 108





	1. Pork soda part 1

**Author's Note:**

> Ironically, the first time I actually wrote classic sans so far

“Hey”

“.....Hey.....”

It was twilight, there. Orange turned to Pink as she pulled him, past the prison and to the seaside cliff. The one where they say lovers die.

“You know, you’d think that they would put a fence here if there were so many injured teens jumping here.”

“Yeah, as if that’ll stop teens for being so edgy”

“Was that pun intentional?”

“Well, then, I guess you can say it was punintentional on my part.” 

God, she was amazing. 

“Hey, what if we....”

“Jumped? Nah, we’re not edgy teens.”

“Speak for yourself, I can cut myself on how edgy I am~ cmon... lets jump.”

“Why do teens even jump? This isn’t Romeo and Juliet, our parents don’t wanna kill each other”

“I don’t know, I think it’s like.... trust fall? Or it’s just romantic? Cmon, I’m gonna. I’m gonna without youuuuu”

“You’re drunk.”

“Not fully~ cmon sans, last chance!”

A leg, hovering over the drop beneath her. 

“Saaaans, don’t let me at a cliff ha-“

He ran into her, both laughing as they fell into the water below.


	2. Pork soda part 2

**Notes for the Chapter:**

> Damn I love writing little tiny vague ass stories

It was a slow night at grillby’s... or maybe it was 3am, either way, Sans couldn’t help but feel even lonelier with the empty seat next to him. Usually she would be here, telling him weird ass shit about the world. Then he’d crack jokes and puns about it and she’d either get mad or laugh and try her even worse jokes. He found himself missing even the ones that don’t land and is confusing. Because at least she would laugh.

Now when he looks at her, he aches. She smiles but it never reaches her eyes, making his ribs tighten and creak. He wised she looked more like she did that night...

He wished they’d jump that cliff again.


	3. Sans’s heat em’ up

He was trying. Really. This was like the most trying he’s ever tried. He was so sure that this was the one alpha for him. If only they’d start picking up on that fact. He’s tried everything! Submitting when she snapped at him, not so subtly showing off his neck whenever she hugged him, fucking laughing when he had his ass up in the air on the bed. 

“Oh haha so funny, you got me sans hahaha-“ He was almost ready to throw himself off the roof but then the familiar tingling went off in his head that told him its time. 

He’s about to go into heat. 

And he doesn’t want to go into this one alone. 

He started by just straight up ripping up his bed, mattress and all. The linens cried in agony, no fabric was safe. Even the clean sheets pap always kept and replaced underneath his bed “FOR YOU TO USE WHEN YOU MAKE YOUR BED” wasn’t safe. 

He moved the treadmill out, his bed out, all the furniture, just in the living room. He needs room to nest. He spent a while just arranging fabric pieces into a nest configuration. But it wasn’t enough. Great start but it’s atrociously not soft. And his mattress wasn’t even that soft to begin with. Just springs inside. He needed fluff. 

That evening, the news covered a wrecked loading truck that was mysteriously robbed of 5 tons of cotton balls. 

“The drivers said one second they were driving, the next they were not. They found the truck twenty minutes after, about a mile away wrecked and empty. All the cotton balls have been stolen but the swans have remained unstolen-“

“THANK STARS, HOW ELSE WOULD I BUY COTTON SWABS IN ORDER TO UNSWAB MY POLISHED NAILS!?!? BROTHER? HAVE YOU HEARD OF TH- OH WAIT, HE’S IN HEAT THAT’S RIGHT. HUMAN, DON’T GO INTO HIS ROOM FOR THE REMAINDER OF THE WEEK!”

You scoffed and reclined more on the couch. “No need to tell me twice. Boundaries? Respected. Doors? Unopened. I am forcibly removing himself for the sake of his privacy.” 

Papyrus grinned and clapped his gloved hands together. “THANK YOU HUMAN! NOW! WE MUST BINGE WATCH THIS SHOW YOU CALL..... H2O???”

“Yeah, it’s a cringey ass show I used to love as a kid but I wanna see it again for nostalgia.... and to make fun of. I thought you’d like it since it shows how crazy we humans thought magic were or something. It’s about these girls who go to a island and goes into this underwater pond or some shit and turn into mermaids and get weird water powers. Reminds me of a YouTube series of rich white 7 year old girls made with their monofins.” You huffed before whispering beneath your breath. “I wanted to be a mermaid-“

“I WANT TO WATCH WHATEVER YOU WANT TO WATCH! EVEN IF IT IS FOR IRONIC PURPOSES!!! PUT IT ON!”

Sans was going to triple no scope himself. His alpha was just outside the door, practically doing nothing! It was so hard not to grab her, pull her in and just go to town. His soul pounded, just urging him to g o. 

An hour went by and Sans literally had to knock himself out to not go out and jump you in front of his brother. 

The next day, Sans was practically becoming the couch. So much of his alpha’s scent was on it! He needed to rub himself all over it. The smell of her made his magic form and now he was humping the sofa. 

Papyrus said nothing but huffed out an exasperated sigh. Seriously? Why can’t Sans take responsibility and approach the alpha by just talking? As always, it’s up to him to do all the dirty work! 

He went back into his room and made a phone call.

“HUMAN! SANS IS HAVING A FIT AND WONT OPEN THE DOOR! PLEASE HELP ME! I THINK HE’D LISTEN TO YOU!!!” 

“FUCK!?!? Uh, I mean OUCH! Sorry, I picked up the phone and then tripped over my coffee table. What were you saying? Sans is a piece of shit? Yeah I kn-“

“JUST COME HERE AT ONCE HUMAN!!!” 

He hanged up. Wowie! They sure are a match. He’s been watching them for months and he could tell the sexual tension between them! Now to set up the scene! 

Papyrus picked up his brother, who was clinging to the cushion you sat on like it was his newborn child, and placed him into his mess of a room. Sans looked up at him with confusion, sweat pouring off of him.

“IF ANYONE SIGNIFICANT COMES IN HERE, SAY THAT YOU HAD A FIT OR SOMETHING OR THAT YOURE NESTING.... ACTUALLY YEAH, SAY YOU WERE NESTING AND YOU DIDNT WANT YOUR GREAT AND POWERFUL BROTHER PAPYRUS TO SEE YOU IN SUCH A STATE. WAIT A MINUTE, YOU ARE NESTING! YOU’RE IN HEAT-“

Papyrus let out an annoyed sound and bonked his skull a few times. 

“JUST! SAY WHATEVER YOU NEED TO SAY! TO HER- I MEAN ANYONE SIGNIFICANT WHOS NOT ME THAT IS COMING INTO YOUR ROOM. POSSIBLY. YES.”

With that, he locked the door before slamming it shut. 

Fuck. What was he talking about? Someone significant? Fuck that, he needed his alpha. With Papyrus gone, Sans took the opportunity to start beating his meat like it owed him money. He dreamt of her hovering above him, taking him roughly as she bred the fuck out of his little soul. He couldn’t wait for them to exchange magic, for her to fill him up and make his soul pastel instead of white. 

He paused when there was knocking at his door. He was about to open it when the entire door got fucking kicked the fuck off, his alpha standing in the doorway looking like a deranged meth addict on crack. Her hair was stringy and greasy, her clothes disheveled and stained with popcorn butter from the night before, her scent wafted throughout the room. It was obvious she didn’t take a shower for at least three days...

Sans has never been so turned on in his life.

“Sans... you’re.... you’re in heat? You’re nesting...”

Magic poured from his mouth as he openly panted, trying to stop pumping his cock but not being able to. He was so close, but he wouldn’t dare cum without his alpha. 

“A-Alpha....”

With that, her eyes grew dark and she walked over, peeling her clothes and flinging it to the edge of the nest. She climbed over him and tore off his clothes, his moans from the harsh treatment echoing into the night. 

Papyrus came home late that morning, wearing a mask so that the oder doesn’t affect him. He’s already made sleeping arrangements with Undyne. He peaks into the room to see Sans and his new Alpha curled up together, naked and still inside each other in their little nest. He’s happy for his brother! 

He just wishes that there’s only one child so Sans won’t commit a crime to get soft materials for a nest again. He already had to get rid of two suspicious bags of empty plastic cotton ball containers.


	4. Egg kustard

**Notes for the Chapter:**

> Sans x reader x sans  
> Poly ftw

Living by yourself in the woods is hard. Maybe that’s why you let two lamias into your life. They weren’t like your usual bitty lamias at the pet store, oh no. These were wild raised in the jungle kind of lamia. 

You were weaving a basket one day because your old one was breaking from overuse. You notice a strange noise coming from behind you, turning around you see a big ass lamia. Oh jeez, the scent of the fresh fish you caught probably attracted it. 

You shrugged and handed it the fish, it’s red eyes widening. It immediately scorfed it down. You gave it another and it scurried away. Interesting. 

The next day, it came back with what you assumed to be it’s mate. Well, you need the company. 

So now your doors are always open and the nights aren’t as cold anymore with two other bodies curled around yours. 

One day though, navy (that’s what you call him because he’s a pretty navy blue) was panting hard. Real hard. Red pushed you out of the house despite your dismay and worry. 

“He’s just in heat.... that means I’ll be in rut soon. You don’t want to be around when it starts unless you’re craving babies in your tummy.”

To be honest, you kinda are. You always enjoy more company, maybe that’s why you watch them as they do their thing. They entwine like a twister and give you a good show of red magic being pumped into blue. You couldn’t help but touch yourself. 

They stayed together for a few minutes before Red pulled out of him, a bit of cum dribbling out of Navy. That was great. 

Red however, turns to you with that sharp grin. 

“It’s your turn. Lemme stretch you out a bit.”

With that, he’s sliding into you. Holding onto your hips, he drives himself home. His other dick rubs against you deliciously. But soon, he pulls out and leaves your empty pussy needing.

“Alright, I got it now.”

Navy replaced Red, his slit opening to reveal a much more longer member. He slides it into you and all you can think about is how squishy it is. It actually slides into your cervix. He moans, panting. 

“You’re gonna take them? Gonna take our babies?”

You couldn’t help but scream yes.

“Fuck, then take then!”

A lump traveled through before pressing against your cervix. As the egg passed the right entrance, it popped and dropped into your womb. You whimpered as Navy kissed all over your face.

“Unf, look at ya, my lil mates, transferring eggs so well.” Red purred, coming up behind you to support you more. 

By the last egg, your stomach is so huge. 

“Fuck, how much did you put in me?”

“Five.”

“That’s.... hah, that’s not as much as I thought it’d be...”

Navy slowly pulled out of you, only for Red to slip back into you. Pressing you down onto him, he licked up your neck. 

“Heh, there would have been more but they’d be way way smaller if we didn’t have so much magic that you fed us.”

He tilted you back just a bit, so he could reach down and kiss you while rolling himself into you again and again. Navy lazily laid on his tail, head dipping down to lick at your clit as Red fucked you. 

“Look at you, our gorgeous human. Gonna give us cute lil hatchlings.” Navy purred as Red panted into your ear, already so close. He moaned as he unloaded into you, crimson magic filling between the spaces of the eggs, rounding out your belly even more. 

“There we go. Just had to make sure they were really fertilized. Can’t wait to have lil souls prancing around.”

You couldn’t agree more.


End file.
